Universal approach to predicting heat transfer coefficient for condensing mini/micro-channel flow

A new universal approach to predicting the condensation heat transfer coefficient for mini/micro-channel flows is proposed that is capable of tackling many fluids with drastically different thermophysical properties and very broad ranges of all geometrical and flow parameters of practical interest. This is accomplished by first amassing a consolidated database consisting of 4045 data points from 28 sources. The database consists of single-channel and multi-channel data, 17 different working fluids, hydraulic diameters from 0.424 to 6.22 mm, mass velocities from 53 to 1403 kg/m2 s, liquid-only Reynolds numbers from 276 to 89,798, qualities from 0 to 1, and reduced pressures from 0.04 to 0.91. An exhaustive assessment of prior correlations shows only two correlations, that are actually intended for macro-channels, provide relatively fair predictions, while mini/micro-channel correlations generally show poor predictions. Two new correlations are proposed, one for predominantly annular flows, and the second for slug and bubbly flows. This approach shows very good predictions of the entire consolidated database, with an overall MAE of 16.0%. It is shown this accuracy is fairly even for different working fluids, and over broad ranges of hydraulic diameter, mass velocity, quality and pressure, and for both single and multiple mini/micro-channels.